1. Field of the Invention
The present invention relates to a temperature management apparatus for managing the temperature of a battery for running mounted on a vehicle such as a hybrid electric vehicle, and a power supply including the temperature management apparatus.
2. Description of Related Art
Recently, hybrid electric vehicles on which an engine and a motor as a power source are mounted have been used. Such a hybrid electric vehicle includes a secondary battery (power supply) as a power source for supplying the driving motor with electric power. The secondary battery is charged or discharged corresponding to the running state of the vehicle.
The secondary battery to be mounted on the hybrid electric vehicle is large and generates a large amount of heat. Furthermore, electrochemical reactions at the time of charging or discharging in the secondary battery rely on temperature. Therefore, when the temperature of the secondary battery exceeds a pre-set temperature, problems can occur. For example, performance of the secondary battery deteriorates or the life is shortened. For preventing these problems, a power supply in a hybrid electric vehicle includes a cooling device for cooling the battery (see JP2003-142166 A, for example).
FIG. 4 is a schematic view showing a configuration of a conventional power supply. The power supply shown in FIG. 4 includes a battery pack 110 and a cooling device. The cooling device feeds air to the interior of the battery pack 110, thereby cooling the battery pack 110 with the air.
Specifically, the battery pack 110 includes a plurality of cells (battery modules) 111 in a battery case 112. An intake 113 for feeding air to the interior and an outlet 114 for exhausting air after a heat exchange are provided for the battery case 112. Furthermore, clearances as channels for the fed air are provided between adjacent cells 111 and between each of the cells 111 and the inner face of the battery case 112.
The cooling device includes an air intake duct 101, an exhaust duct 102 and a fan unit 103. The air intake duct 101 connects the intake 113 of the battery case 112 and an air intake port 109 provided to an interior panel 108 of the vehicle. At the opening of the air intake duct 101 at the side facing the air intake port 109, a filter member 107 is arranged for preventing entry of foreign matters into the battery pack 110.
The exhaust duct 102 connects the outlet 114 of the battery case 112 and an air inlet 103a of the fan unit 103. The fan unit 103 includes a housing 106, a fan 104 arranged inside the housing 106 and a motor 105 for driving the fan 104. An air inlet 103a and an air outlet 103b are provided for the housing 106.
When the fan 104 is driven by the motor 105, air inside the vehicle is fed into the battery case 112 through the air intake duct 101, so that the temperature rising in the respective cells 111 is suppressed. The air warmed by the cells 111 passes through the exhaust duct 102 and is exhausted outside the vehicle through the air outlet 103b provided for the housing 106 of the fan unit 103.
Furthermore, the cooling device shown in FIG. 4 includes a control device 120. The control device 120 includes a deciding part 121, a motor driving part 122 and a temperature detecting part 123, and switches in stages the fan speed (rotation number: ‘rpm’) of the fan 104 in accordance with the temperature of the cells 111 (for example, ‘LOW’, ‘MIDDLE’, and ‘HIGH’).
Specifically, the temperature detecting part 123 detects temperature on the basis of signals from respective temperature sensors 124 attached to the cells 111. The deciding part 121 takes the highest temperature (battery maximum temperature) from the respective detected temperatures, and decides whether the present fan speed is suitable for the battery maximum temperature.
Upon deciding the fan speed as not suitable, the deciding part 121 selects a suitable fan speed with respect to the detected temperature. Furthermore in this case, the deciding part 121 outputs a signal (fan speed direction signal) to the motor driving part 122 so that a voltage corresponding to the selected fan speed is applied to the motor 105.
The motor driving part 122 switches in stages the voltage to be applied to the motor 105 in accordance with the direction from the deciding part 121 so as to adjust in stages the fan speed of the fan 104. Therefore, when the deciding part 121 outputs the fan speed direction signal, the motor driving part 122 switches the voltage so that the fan 104 will rotate at a selected fan speed.
In this manner, the control device 120 drives the fan 104 while switching the fan speed in stages in order to prevent the temperature of the cells 111 from exceeding a pre-set threshold value, thereby suppressing temperature rising of the cells 111.
However, in the case of the cooling device as shown in FIG. 4, since the temperature sensors 124 are attached only to the cells 111, the control device 120 controls the fan speed of the fan 104 on the basis of the temperature of the cells 111 alone.
Therefore, for example, as shown in FIG. 5, in a case where the vehicle is kept in the direct sun and the temperature of the cells 111 is raised, even when the temperature inside the vehicle becomes higher than the temperature of the cells 111, the control device 120 drives the fan 104. As a result, as indicated as an area B surrounded by a broken line in FIG. 5, the temperature of the cells 111 is raised instead to degrade the performance of the battery.
FIG. 5 is a graph showing a control by a conventional cooling device. FIG. 5 indicates changes in the ambient temperature and the battery temperature, and an operating condition of the fan in a case where the vehicle is kept in the direct sun. The term ‘ambient temperature’ in FIG. 5 indicates a temperature of air introduced into the battery case 112 through the air intake duct 101, while the same term for the cooling device in FIG. 4 indicates the temperature inside the vehicle. The term ‘battery maximum temperature’ in FIG. 5 denotes a highest value for the battery temperatures detected on the basis of signals from the respective temperature sensors 124, and the ‘battery minimum temperature’ denotes a lowest temperature for the battery temperatures detected on the basis of signals from the respective temperature sensors 124.
When the vehicle is kept under a condition where the outside temperature is low and the temperature of the cells 111 is lowered, the control device 120 does not drive the fan 104. Therefore, even if the interior of the vehicle is warmed by heating, the warmed air inside the vehicle will not be introduced into the battery case 112. Therefore in this case, the cells 111 cannot exhibit the desired performance until the temperature is raised by self-heating.